It's called liquidity preference. No matter how rich you are, there is no downside to being liquid but severe downsides to being illiquid so having extra money,

It's called liquidity preference. No matter how rich you are, there is no downside to being liquid but severe downsides to being illiquid so having extra money, no matter whether you use it in practice or not, is always worth it, just in case something useful ever pops up. This also means the interest rate gets stuck at some positive value and "investment philanthropy" never happens. If people use net worth or money as a highscore or status symbol that would also be considered liquidity preference.